The Colours and Pigments of Butterflies. 



By M. I. Nbwbigin, D.Sc. 



In a previous issue of Natural Science, in the course of a paper on 

 " The Pigments of Animals," an account of the general colour-pheno- 

 mena of the Lepidoptera was given, and the great interest and import- 

 ance of the subject indicated. Since the publication of that paper, not 

 a few observers have been engaged in pursuing further investigations, 

 and numerous additional papers have appeared ; some of these it is 

 proposed to briefly summarise here. For a somewhat detailed account 

 of the papers published up to the end of last year, reference may be 

 made to the chapters on the subject in my " Colour in Nature " (1898), 

 but preparatory to the consideration of more recent work, the results of 

 these earlier observations may be very briefly stated here. 



The researches of Hopkins, Spuler, Urech, Mayer, and many others 

 have shown — (1) that the colours of the wings in butterflies are due 

 sometimes to pigments, sometimes to optical effects, and sometimes to 

 a combination of the two ; (2) that pigmental colours are shades of 

 yellow, red, deep brown, or rarely white, green, and pure black; (3) that 

 the white, yellow, and red pigments of the Pieridae, and possibly of other 

 butterflies, are members of the uric acid group ; (4) that the red, 

 yellow, and white pigments at least in the Pieridae are chemically 

 nearly related, while the black and brown pigments differ markedly 

 from them, and are of unknown chemical relations. Further, it has 

 been noticed by several different observers that, in the development of 

 colour in the pupa, white or yellow tints first appear, and there is 

 then a gradual darkening of tint as development proceeds — black 

 always being the last tint to appear. 



Of the more recent papers with which we are concerned here, we 

 shall take first one by Dr. M. Baer on the minute structure of the 

 wing-scales in diurnal Lepidoptera. In its general outline, the paper 

 for the most part merely confirms the results of others, but on several 

 points it is more detailed, and it is valuable as a clear statement of the 

 general characters of the colours of butterflies and their causes. The 

 value of the paper is greatly increased by the fact that the author did 

 not confine his observations to one family, and therefore is enabled to 



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